Modular light-emitting panel assembly

ABSTRACT

A modular light-emitting panel assembly has first and second light guides edge lit by respective light sources. Each light guide has a light input edge, opposed side edges, opposed major surfaces and a pattern of light extracting elements at at least one of the major surfaces. The light guides are juxtaposed with a side edge of the first light guide abutting a side edge of the second light guide at a seam and with the major surfaces nominally coplanar. Various embodiments of the panel assembly additionally include respective structures that reduce visibility of the seam when the light sources illuminate the panel assembly.

RELATED APPLICATION DATA

This application is a continuation of U.S. patent application Ser. No.14/352,844, filed Apr. 18, 2014, which is a national phase ofInternational Application No. PCT/US2012/057837, filed Sep. 28, 2012,which claims the benefit of U.S. Patent Application No. 61/549,489 filedOct. 20, 2011, the disclosures of which are incorporated herein byreference in their entirety.

BACKGROUND

Modular light-emitting panel assemblies having multiple edge-lit lightguides arranged side-by-side are known. However, the light output fromknown modular light-emitting panel assemblies typically has anon-uniform intensity profile, especially at the seams where the lightguides abut.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view showing an example of anembodiment of a modular light-emitting panel assembly.

FIG. 1B is a cross-sectional view showing the modular light-emittingpanel assembly shown in FIG. 1A.

FIGS. 2A and 2B are perspective and plan views, respectively, showingthe modular light-emitting panel assembly shown in FIG. 1A with thediffuser plate and the optical films removed.

FIG. 3 is an exploded front view showing an example of two adjacentlight guides having substantially planar side edges orthogonal to themajor surfaces of the light guides.

FIG. 4 is a cross-sectional view showing an example of anotherembodiment of a modular light-emitting panel assembly having taperedlight guides.

FIG. 5 is a plan view showing an example of another embodiment of amodular light-emitting panel assembly.

FIG. 6 is a plan view showing an example of another embodiment of alight-emitting panel assembly in which the light source for each lightguide has a single solid-state light emitter.

FIG. 7 is a plan view showing an example of another embodiment of amodular light-emitting panel assembly in which the light source for eachlight guide has three solid-state light emitters.

FIGS. 8A and 8B are exploded perspective and perspective views,respectively, showing part of an example of a simplified embodiment of amodular light-emitting panel assembly in which a thin strip of film isinterposed between adjacent side edges of the light guides to reducevisibility of the seam when the panel assembly is illuminated.

FIG. 9 is a perspective view showing part of an example of a simplifiedembodiment of a modular light-emitting panel assembly in which anelongate film strip covers the seam to reduce visibility of the seamwhen the panel assembly is illuminated.

FIGS. 10A and 10B are perspective and front views, respectively, showingpart of an example of a simplified embodiment of a modularlight-emitting panel assembly that includes an example of a lightredirecting element to reduce visibility of the seam when the panelassembly is illuminated.

FIG. 11 is a front view showing part of an example of a simplifiedembodiment of a modular light-emitting panel assembly that includesanother example of a light redirecting element to reduce visibility ofthe seam when the panel assembly is illuminated.

FIG. 12 is a front view showing an example of a simplified embodiment ofa modular light-emitting panel assembly that includes another example ofa light redirecting element to reduce visibility of the seam when thepanel assembly is illuminated.

FIG. 13 is a front view showing an example of a simplified embodiment ofa modular light-emitting panel assembly that includes another example ofa light redirecting element to reduce visibility of the seam when thepanel assembly is illuminated.

FIG. 14 is a front view showing an example of a simplified embodiment ofa modular light-emitting panel assembly that includes another example ofa light redirecting element to reduce visibility of the seam when thepanel assembly is illuminated.

FIG. 15 is a front view showing an example of a simplified embodiment ofa modular light-emitting panel assembly that includes another example ofa light redirecting element to reduce visibility of the seam when thepanel assembly is illuminated.

FIG. 16 is an exploded front view showing an example of a simplifiedembodiment of a modular light-emitting panel assembly that includeslight guides having non-orthogonal side edges to reduce visibility ofthe seam when the panel assembly is illuminated.

FIG. 17 is an exploded front view showing an example of a simplifiedembodiment of a modular light-emitting panel assembly having an exampleof non-planar side edges of the light guides.

FIG. 18 is an exploded front view showing an example of a simplifiedembodiment of a modular light-emitting panel assembly having anotherexample of non-planar side edges of the light guides.

FIG. 19 is a perspective view showing part of an example of anothersimplified embodiment of a modular light-emitting panel assembly inwhich the back reflector includes a visibility-reducing pattern toreduce visibility of the seam when the panel assembly is illuminated.

FIG. 20 is a perspective view showing part of an example of anothersimplified embodiment of a modular light-emitting panel assembly thatincludes a transparent plate juxtaposed with the front major surface ofthe light guides to reduce visibility of the seam when the panelassembly is illuminated. The transparent plate includes a pattern oflight diverting elements aligned with the seam.

FIG. 21 is a perspective view showing part of an example of anothersimplified embodiment of a modular light-emitting panel assemblyincluding a transparent plate having a visibility-reducing pattern inalignment with the seam juxtaposed with the front major surfaces oflight guides, and a back reflector having a visibility-reducing patternin alignment with the seam juxtaposed with the back major surfaces ofthe light guides to reduce visibility of the seam when the panelassembly is illuminated.

FIGS. 22A-22D are plan views showing part of an example of a progressivescanning sequence that can be implemented using the modularlight-emitting panel assembly embodiments described herein.

FIGS. 23A-23D are plan views showing part of another example of aprogressive scanning sequence that can be implemented using the modularlight-emitting panel assembly embodiments described herein.

FIG. 24 is an exploded view showing an example of active dimming thatcan be implemented using the modular light-emitting panel assemblyembodiments described herein.

DETAILED DESCRIPTION

FIGS. 1A and 1B are exploded perspective and cross-sectional views,respectively, showing an example of an embodiment of a modularlight-emitting panel assembly 200 that includes light guides. Modularlight-emitting panel assembly 200 includes a tray 205 that houses lightguides 210. Referring to FIG. 1A, the tray 205 has a base 211, a firstside wall 212 and a second side wall 213 opposite the first side wall.First side wall 212 and second side wall 213 extend from base 211. Tray205 additionally has a third side wall 214 a and a fourth side wall 214b, opposite the third side wall. Third side wall 214 a and fourth sidewall 214 b also extend from base 211. In the example shown, base 211,first side wall 212, second side wall 213, third side wall 214 a, andfourth side wall 214 b extend orthogonally to base 211. Together, thefirst and second side walls 212, 213 define the width W of tray 205between them. Similarly, the third and fourth side walls 214 a,b definethe length L of tray 205 between them.

In the illustrated embodiment, modular light-emitting panel assembly 200includes nine light guides 210 a-i. In this disclosure, referencenumerals without appended letters refer to corresponding elementsgenerically whereas reference numerals with appended letters refer tospecific ones of the corresponding elements. Each light guide 210 cantake the form of, and can include one or more of the features of thelight guides described and illustrated in U.S. Pat. No. 6,712,481. Eachlight guide 210 has at least one light output surface that constitutesat least part of one of the major surfaces of the light guide. Eachlight guide 210 additionally includes a pattern of light extractingoptical elements (not shown) that extract light propagating within thelight guide through each light output surface. Although the illustratedembodiment of modular light-emitting panel assembly 200 includes ninelight guides 210, other embodiments of panel assembly 200 have more orfewer than nine light guides.

As described above, each of the light guides 210 is generally planar inshape and has a greater cross-sectional width than thickness.Additionally, each of the light guides 210 has a greater length thanwidth. With reference to FIGS. 1B and 2B, a first light guide 210 a hasa front major surface 215 a and a back major surface 220 a opposite thefront major surface that define the thickness t of the light guidebetween them. Light guide 210 a additionally has a first side edge 225 aand a second side edge 230 a opposite first side edge 225 a that definethe width W of light guide 210 a between them. Light guide 210 aadditionally has a light input edge 235 a and an end edge 240 a oppositelight input edge 235 a that define the length L of light guide 210 abetween them. The remaining light guides 210 b-i of modularlight-emitting panel assembly 200 have the same structure as light guide210 a and will not be individually described.

In the embodiment shown, the first and second side edges 225, 230 ofeach of the light guides 210 are substantially planar and are orientedsubstantially orthogonally to the front and back major surfaces 215,220, as shown in FIG. 3. In other embodiments, the first and second sideedges 225, 230 of each of the light guides 210 are configureddifferently, as will be described below.

In the embodiment of modular light-emitting panel assembly 200 shown inFIGS. 1A and 1B, each of the light guides 210 has a uniform thicknessalong its length. In another embodiment, shown in FIG. 4, a modularlight-emitting panel assembly 200′ includes light guides 210′ eachhaving a thickness t that decreases with increasing distance from itslight input edge 235′.

In the embodiment shown in FIGS. 1A, 1B, 2A and 2B, light guides 210 arearranged in a side-by-side relationship to each other, such that thefirst side edge 225 of one of the light guides abuts the second sideedge 230 of an adjacent light guide such that the front major surfaces215 of the light guides 210 are coplanar and collectively form a single,step-less front major surface of modular light-emitting panel assembly200. In some embodiments, light guides 210 are positioned such that theside edges of adjacent light guides that abut are in contact with eachother. Together, the side edges of adjacent light guides that abut forma seam between the adjacent light guides. For example, as shown in FIGS.2A and 2B, the first side edge 225 b of second light guide 210 b abutsthe second side edge 230 a of first light guide 210 a. The first sideedge 225 b and second side edge 230 a collectively form a seam 245 abetween first light guide 210 a and second light guide 210 b. Theabutting side edges of the other adjacent light guides 210 form sevenother seams 245 b-h in the panel assembly 200.

In the embodiment shown, light guides 210 are installed in tray 205 withthe first and second side edges 225, 230 of the light guides parallel tothe third side wall 214 a and the fourth side wall 214 b of the tray.The length L_(p) of the light guides 210 is similar to, but less than,the length L of tray 205, as shown in FIG. 2B. In another embodiment,shown in FIG. 5, light guides 210″ are installed in tray 205 with thefirst and second side edges 225″, 230″ of the light guides 210″ parallelto the first and second side walls 212″, 213″ of the tray. In thisembodiment, the length L_(p) of the light guides 210″ is similar to, buttypically slightly less than, the width W of the tray.

In another embodiment (not shown), the length of each of the lightguides is slightly less than one-half of the length L of tray 205. Eachof the light guides has a light source (described in more detail below)at its light input edge 235. The light guides are installed in the trayin pairs, with the light source of one light guide of each pair adjacentthe first side wall 212 of tray 205, and with the light source of theother of light guide of each pair adjacent the second side wall 213 ofthe tray. In another embodiment (not shown), the length of each of thelight guides is slightly less than one-half of the width W of tray 205.Each of the light guides has a light source at its light input edge 235.The light guides are installed in the tray in pairs, with the lightsource of one light guide of each pair adjacent the third side wall 214a of tray 205, and with the light source of the other of light guide ofeach pair adjacent the fourth side wall 214 b of the tray.

In modular light-emitting panel assembly 200, each of the light guides210 is edge lit by a respective light source 250. Light source 250 isoptically coupled to the light input edge 235 of the light guide suchthat light emitted by the light source enters the light guide andtravels along the light guide by total internal reflection at the majorsurfaces. Light source 250 includes solid-state light emitters such aslight-emitting diodes (LEDs), laser diodes, and organic LEDs (OLEDs). Inan embodiment in which light source 250 includes LEDs, the LEDs may betop-fire LEDs or side-fire LEDs, and may be broad-spectrum LEDs (e.g.,emit white light), LEDs that emit light of a desired color (e.g., redlight, green light, blue light, or ultraviolet light, infrared light),or a mixture of broad-spectrum LEDs and LEDs that emit monochromaticlight of a desired color. In one embodiment, light source 250 emitslight with no operably-effective intensity at wavelengths greater than500 nanometers (nm), i.e., the light source emits light at wavelengthsthat are predominantly less than 500 nm. In such embodiments, phosphors(not shown) convert at least part of the light emitted by light source250 to longer-wavelength light. Light source 250 may constitute part ofa light source assembly (not shown) that also includes structuralcomponents (e.g., a printed circuit board (PCB)) (not shown) to retainlight source 250 and to locate the light source relative to respectivelight guide 210. The light source assembly may additionally includecircuitry, power supply and/or electronics for controlling and drivinglight source 250, a heat sink, and other appropriate components.

In the embodiment shown in FIGS. 1A, 1B, 2A and 2B, the light source 250for each light guide 210 in modular light-emitting panel assembly 200 iscomposed of two solid-state light emitters 252. The solid-state lightemitters 252 constituting the respective light source 250 are positionedadjacent the light input edge 235 of each light guide 210 and areconfigured to direct light into the light guide 210 within a range ofangles such that the light propagates along the light guide 210 by totalinternal reflection at the front and back major surfaces 215, 220. Thelight input edge 235 of each light guide 210 may be configured to spreadthe light received from the solid-state light emitters 252 across thewidth W of each light guide 210. In an example, each input edge 235includes refractive surfaces or a lens array configured to spread thelight from the solid-state light emitter 252 to a greater extentwidthwise than heightwise. Additionally or alternatively, light inputedge 235 can include one or more optically polished areas,anti-reflection areas, textured areas, lensed areas, prismatic areas orany combination of the above to condition the light entering the lightguide. Although in the embodiment of panel assembly 200 shown in FIGS.1A, 1B, 2A, 2B, light source 250 for each light guide 210 is composed oftwo solid-state light emitters 252, other configurations of light source250 are possible. In the embodiment shown in FIG. 6, the light source250 for each of the light guides 210 is composed of a single solid-statelight emitter 252. Single solid-state light source 252 is typically anLED that generates white light. In the embodiment shown in FIG. 7, thelight source 250 for each of the light guides 210 is composed of threesolid-state light emitters 252. In an example, the solid-state lightemitters are LEDs that respectively generate red, green and blue light.Solid-state light emitters 252 may be operated simultaneously orsequentially. In other embodiments (not shown), the light source 250 foreach of the light guides 210 is embodied as more than three solid-statelight emitters, or, as mentioned above, by different combinations ofLEDs or other solid-state light emitters.

Referring again to FIGS. 1B and 2B, modular light-emitting panelassembly 200 also includes an end reflector 255 and two side reflectors260 a,b. End reflector 255 faces the end edges 240 of light guides 210.Side reflector 260 a faces the first side edge 225 a of first lightguide 210 a. Side reflector 260 b faces the second edge 230 i of theninth light guide 210 i. Additionally, the panel assembly 200 includes aback reflector 265 facing the back major surfaces 220 of light guides210, as shown in FIG. 1B.

In the example shown, end reflector 255, side reflectors 260 a, 260 band back reflector 265 are each embodied as separate components. Endreflector 255 is interposed between the end edges 240 of light guides210 and the second side wall 213 of tray 205. Side reflector 260 a isinterposed between the side edge 225 a of light guide 210 a and thethird side wall 214 a of tray 205. Side reflector 260 b is interposedbetween the side edge 230 i of light guide 210 i and the fourth sidewall 214 b of tray 205. Back reflector 265 is interposed between theback major surfaces 220 of light guides 210 and the base 211 of tray205.

In another embodiment (not shown), one or more of end reflector 255,side reflectors 260 a, 260 b, and back reflector 266 are integral withtray 205. In an example, the internal surfaces of the tray 205 are madereflective or partially reflective to act as end reflector 255, sidereflectors 260 a, 260 b, and/or back reflector 265. In anotherembodiment (not shown), one or more of end reflector 255, sidereflectors 260 a, 260 b, and back reflector 266 are integral withportions of light guides 210. In an example, the above-mentionedreflectors are provided by reflective coatings on the end edges 240 andback major surfaces 220 of all the light guides 210, and on the sideedge 225 a of light guide 210 a and the side edge 230 i of light guide210 i.

In the embodiment shown in FIG. 4, a tray 205′ has a base 211′ that isangled to correspond to the taper of light guides 210′. In thisembodiment, back reflector 265′ rests on base 211′ to ensure that itsits flush against the back major surfaces 220′ of light guides 210′.

In the embodiment shown in FIGS. 1A, 1B, 2A, 2B, modular light-emittingpanel assembly 200 additionally includes a diffuser 270 supported by thethird and fourth side walls 214 a, 214 b of tray 205 parallel to thefront major surfaces 215 of light guides 210, as shown in FIG. 1A.Diffuser 270 is configured as a film or a plate. Diffuser 270 isconfigured to diffuse the light extracted from light guides 210 toprovide a smoother light output distribution from panel assembly 200. Asshown in FIG. 1B, diffuser 270 is spaced from light guides 210 toprovide a light mixing space 275 between the light guides and thediffuser. The size of light mixing space 275 in a direction orthogonalto the front major surfaces 215 of light guides 210 is made sufficientto allow for any needed color mixing of the light extracted from thepanel members to occur. Additionally or alternatively, as discussed inmore detail below, the size of light mixing space 275 can be madesufficient to reduce the visibility of the seams 245 between adjacentones of the light guides. Optical layers 280 a, 280 b are locatedadjacent diffuser 270. Optical layers 280 a, 280 b are configured toredirect the light transmitted through the diffuser in a predeterminedmanner. The optical layers are typically configured as optical films.One suitable example of an optical film is Vikuiti® BrightnessEnhancement Film sold by 3M Company, St. Paul, Minn., USA. In otherembodiments (not shown), modular light-emitting panel assembly 200 hasno optical layers, one optical layer, or more than two optical layers.Examples of optical layers include prismatic films, lenticular films,polarizer films, reflective polarizer films, diffuser films, or otherfilms or plates that redirect, recycle or diffuse light.

When light sources 250 edge light modular light-emitting panel assembly200, the light extracted through the front major surfaces 215 of lightguides 210 has an intensity profile, i.e., a measure of intensity withposition on the combined front major surfaces of the light guides.Substantial positional variations in intensity can occur at the seams245 between adjacent light guides. A sharp spike in intensity caused byunwanted light emitted from the seam causes the intensity variation atthe seam. A spike in intensity at a seam 245 is the result of unwantedlight extracted from adjacent light guides 210 in the vicinity of theseam. Imperfections in the side edges 225, 230 of light guides 210, andin the corners between the side edges and the major surfaces 215, 220 ofthe light guide extract unwanted light from the light guide. At leastsome of the unwanted light is directed towards the observer and may beobserved by the observer as an intensity spike.

In some applications, visibility of seams 245 is acceptable, or evendesirable. However, in most applications (e.g., when the panel assemblyis to be used as a backlighting assembly for a liquid crystal display(LCD)), visibility of seams 245 is undesirable. Reduction in thevisibility of intensity variations at the seams is desirable in suchapplications. To simplify the following description, visibility ofintensity variations at the seams between adjacent light guides will bereferred to herein as visibility of the seams. Visibility of the seamscan be reduced by increasing the size of light mixing space 275.However, increasing the size of the light mixing space increases thethickness of the panel assembly 200, which is undesirable as currentmarket demand is for thin panel assemblies. Accordingly, the variousembodiments of modular light-emitting panel assembly 200 disclosedherein are each configured to reduce the visibility of the seams whileusing a light mixing space 275 small enough for the panel assembly tosatisfy market demand for thin panel assemblies. Configurations ofmodular light-emitting panel assembly 200 that reduce the visibility ofthe seams when the panel assembly is illuminated will now be described.

In the following descriptions of various embodiments of modularlight-emitting panel assembly 200, the drawings show and the descriptiondescribes a simplified embodiment of panel assembly 210 composed of onlytwo light guides 210 a, 210 b to simplify the drawings and thedescription. Moreover, to enable the drawings to show more detail, onlyportions of light guides 210 a, 210 b adjacent their respective lightsources 250 a, 250 b are shown. However, the drawings and descriptionherein additionally apply to embodiments of panel assembly 200 having agreater number of light guides.

FIGS. 8A and 8B show part of an example of a simplified embodiment ofmodular light-emitting panel assembly 200 configured to reducevisibility of seams between adjacent light guides when the panelassembly is illuminated. FIG. 8A is an exploded view. FIG. 8B is anon-exploded view. In the embodiment shown in FIGS. 8A and 8B, a thinstrip of film 305 is interposed between the adjacent side edges 230 a,225 b of light guides 210 a, 210 b, respectively. Film 305 separates theside edges 230 a, 225 b of light guides 210 a, 210 b, respectively, fromone another.

In one embodiment, film 305 is a diffuser film that diffuses unwantedlight emitted from seam 245 a towards the observer. Diffusing theunwanted light reduces the amount of the unwanted light directed towardsthe observer from the seam. Thus, film 305 embodied as a diffusing filmperforms the function of reducing the visibility of the seam. Onesuitable example of a diffuser film that can be used as film 305 inmodular light-emitting panel assembly 200 is D114 SIII sold by TsujidenCo., Ltd., Tokyo, Japan.

In another embodiment, film 305 is a light-absorbing film such as aneutral-density film. The light-absorbing film absorbs unwanted lightemitted from seam 245 a towards the observer, which reduces visibilityof the unwanted light to the observer. Thus, film 305 embodied as aneutral-density film performs the function of reducing the visibility ofthe seam. One example of a neutral density film suitable for use as film305 in panel assembly 200 is 8210 ND sold by Lee Filters USA, Burbank,Calif., USA.

In another embodiment, film 305 is a prismatic film. The prismatic filmis configured to redirect the unwanted light emitted from seam 245 atowards the observer in other directions that reduce visibility of theunwanted light to the observer. Such directions are non-orthogonal tothe major surfaces of the light guides. The prismatic film has grooves(not shown) and is installed between light guides 210 a, 210 b with thegrooves orthogonal to the front major surface 215 of the light guides.With the groove orientation as described, the prismatic film redirectspart of the unwanted light emitted from seam 245 a along the seam andredirects another part of the unwanted light emitted from the seam backinto the light guides. Redirected as just described, the unwanted lightis less visible to the observer. Thus, film 305 embodied as a prismaticfilm performs the function of reducing the visibility of the seam. Oneexample of a prismatic film suitable for use as film 305 in panelassembly 200 is BEF II 90/50 sold by 3M Company, St. Paul, Minn., USA.

In another embodiment, film 305 is a specularly-reflective ordiffusely-reflective film. A reflective film reflects unwanted lightemitted from seam 245 a towards the observer in directions that reducevisibility of the unwanted light to the observer. Such directions arenon-orthogonal to the major surfaces of the light guides. Thus, film 305embodied as a reflective film performs the function of reducing thevisibility of the seam. One example of a reflective film suitable foruse as film 305 in panel assembly 200 is Vikuiti® ESR sold by 3MCompany, St. Paul, Minn., USA. In some embodiments, film 305 is affixedto one or both of the abutted side edges 230 a, 225 b of light guides210 a, 210 b, respectively.

FIG. 9 shows part of an example of another simplified embodiment ofmodular light-emitting panel assembly 200. In the embodiment shown, theadjacent side edges 230 a, 225 b of exemplary light guides 210 a, 210 b,respectively, abut at a seam 245 a, and panel assembly 200 additionallyincludes an elongate strip of film covering seam 245. The strip of filmwill be referred to herein as a film strip 310. Film strip 310 isattached to one or both light guides 210 with its major surface parallelto the front major surface 215 of the light guides. In one embodiment,film strip 310 is a strip of any of the above-described diffuser films.Film strip 310 embodied as a strip of diffuser film redistributesunwanted light emitted from seam 245 a towards the observer in otherdirections that reduce visibility of the unwanted light to the observer.Such directions are non-orthogonal to the major surfaces of the lightguides. Thus, film strip 310 embodied as a diffuser film performs thefunction of reducing visibility of the seam.

In another embodiment, film strip 310 is a strip of any of theabove-mentioned light absorbing films. Film strip 310 embodied as astrip of light absorbing film that absorbs unwanted light emitted fromseam 245 a towards the observer to reduce visibility of the unwantedlight to the observer. Thus, film strip 310 embodied as alight-absorbing film performs the function of reducing visibility of theseam.

In another embodiment (not shown), panel assembly 200 includes a sheetof transparent film sized to cover the front major surfaces 215 of lightguides 210 a, 210 b. The transparent film has an elongate opaque ordiffusing region that covers a seam 245 a and functions similarly tolight absorbing or diffusing film strip 305. Thus, a transparent filmthat covers the light guides and has an elongate opaque or diffusingregion covering seam 245 a performs the function of reducing visibilityof the seam. Moreover, in a non-simplified embodiment of panel assembly200 having more than two light guides 210, the sheet of transparent filmis sized to cover the front major surfaces 215 of all the light guides210. The transparent film has multiple elongate opaque or diffusingregions. A respective one of the elongate opaque or diffusing regionscovers each seam 245 and functions similarly to a respective absorbingor diffusing film strip 305. Thus, a transparent film that covers thelight guides and has a respective elongate opaque or diffusing regioncovering each seam 245 performs the function of reducing visibility ofthe seam.

In another embodiment, film strip 310 is a strip of any of theabove-mentioned prismatic films. Film strip 310 embodied as a strip ofprismatic film redirects unwanted light emitted from seam 245 a towardsthe observer to other directions that reduce visibility of the unwantedlight to the observer. Such directions are non-orthogonal to the majorsurfaces 215 of the light guides 210. Thus, film strip 310 embodied as aprismatic film performs the function of reducing visibility of the seam.In an example in which the prismatic film is a 90° prismatic film, thegrooves of the prismatic film face towards the front major surfaces 215of the light guides 210.

In another embodiment, film strip 310 is a strip of any of thereflective films described above. Film strip 310 embodied as a strip ofreflective film reflects unwanted light emitted from seam 245 a towardsthe observer to other directions that reduce visibility of the unwantedlight to the observer. Such directions are non-orthogonal to the majorsurfaces 215 of the light guides. Thus, film strip 310 embodied as areflective film performs the function of reducing visibility of theseam.

In another embodiment, one or both the abutting side edges 225 a, 225 bof adjacent light guides 210 have a coating thereon. In one embodiment,the coating is an anti-reflective coating. The anti-reflective coatingreduces the amount of light reflected by the side edges 225 a, 225 b oflight guides 210 towards the observer as unwanted light. This reducesvisibility of the unwanted light to the observer. Thus, ananti-reflective coating on one or both abutting side edges 225 a, 225 bperforms the function of reducing visibility of the seam.

In another embodiment, the coating is a specularly-reflective ordiffusely-reflective coating such as a silver or white reflectivecoating. The reflective coating reflects unwanted light emitted fromseam 245 towards the observer in directions that reduce visibility ofthe unwanted light to the observer. Thus, a coating on one or bothabutting side edges 225 a, 225 b performs the function of reducingvisibility of the seam.

In another embodiment, one or both of the side edges 225 a, 225 b ofadjacent light guides 210 a, 210 b includes refractive or refractivestructures. Such structures reflect or refract unwanted light emittedfrom seam 245 a towards the observer in directions that reducevisibility of the unwanted light to the observer. Thus, refractive orrefractive structures on one or both abutting side edges 225 a, 225 b oflight guides 210 a, 210 b perform the function of reducing visibility ofthe seam. In another embodiment, one or both of the side edges 225 a,225 b of adjacent light guides 210 a, 210 b includes one or moreoptically polished areas, textured areas, lensed areas, prismatic areasor any combination thereof.

In another embodiment, the side edges 225 a, 225 b of adjacent lightguides 210 a, 210 b are bonded together using an optical-grade adhesiveor index-matched adhesive. The optical-grade adhesive has an index ofrefraction equal to that of the material of the light guides. Equalrefractive indices include refractive indices that differ by up to ±0.1.One example of an optical-grade adhesive suitable for use with acryliclight guides is OP-21 sold by DYMAX Corporation, Torrington, Conn., USA.Other examples of an optical-grade adhesive include optically-clearsilicone adhesives, including solvent-based and UV-curable adhesives.Bonding the adjacent side edges 225 a, 225 b of light guides 210together with optical-grade adhesive or an index-matched adhesivereduces the amount of light reflected by the side edges towards theobserver as unwanted light. This reduces visibility of the unwantedlight to the observer. Thus, optical-grade adhesive or an index-matchedadhesive bonding the adjacent side edges 225 a, 225 b of light guides210 together performs the function of reducing visibility of the seam.

In some embodiments, modular light-emitting panel assembly 200 includesa light redirecting element adjacent seam 245 a and configured toredirect unwanted light emitted from seam 245 a towards the observer indirections that reduce visibility of the unwanted light to the observer.Thus, a light redirecting element adjacent seam 245 a configured toredirect unwanted in directions that reduce visibility of the unwantedlight to the observer performs the function of reducing visibility ofthe seam.

FIGS. 10A and 10B are perspective and front views, respectively, showingpart of an example of another embodiment of a panel assembly thatincludes a light redirecting element 315. In the example shown, lightredirecting element 315 is configured as an elongate triangular prismwith the apex of the prism aligned with and facing seam 245 a. Lightredirecting element 315 is transmissive or opaque, and one or more ofits surfaces may be reflective. In this embodiment, light redirectingelement 315 reflects unwanted light emitted from seam 245 towards theobserver. The unwanted light is incident on the two sides of thetriangular prism facing the light guides 210 a, 210 b and is reflectedby the prism in sideways directions that reduce visibility of theunwanted light to the observer. Thus, a light redirecting elementembodied as an elongate triangular prism with its apex aligned with theseam performs the function of reducing visibility of the seam.

In other examples, light redirecting element 315 has a cross-sectionalshape different from the triangular cross-sectional shape shown in FIGS.10A and 10B. Examples of other cross-sectional shapes include a“T”-shaped cross-sectional shape where the base of the “T” shape facesseam 245 a as shown in FIG. 11; a cross-sectional shape bounded by achord and an intersecting arc of a curve, where the arc is aligned withand faces seam 245 a as shown in FIG. 12; a rectangular cross-sectionalshape having a grooved surface (e.g., a V-grooved surface or alenticular grooved surface) that faces seam 245 a as shown in FIG. 13; atriangular cross-sectional shape where the apex of the triangle isaligned with and faces seam 245 a and the surfaces that form the apexare concave as shown in FIG. 14; and a cross-sectional shape bounded bya chord and an intersecting arc of a curve, where the chord is alignedwith and faces seam 245 a as shown in FIG. 15. In the example shown inFIG. 15, light redirecting element 315 is configured as a plano-convexcylindrical lens that refracts unwanted light emitted from seam 245 atowards the observer in directions other than a direction orthogonal tothe front surfaces 215 of light guides 210. In another embodiment, thelight redirecting element 315 has a complex geometry that refractsand/or reflects unwanted light incident thereon in directions orthogonalto the front major surfaces 215 of light guides 210. Thus, a lightredirecting element aligned with the seam and (a) having a T-shapedcross-sectional shape where the base of the “T” shape faces the seam,(b) having a rectangular cross-sectional shape with a grooved surfacefacing the seam, (c) having a triangular cross-sectional shape withstraight or concave surfaces facing the seam, (d) having across-sectional shape bounded by a chord and an intersecting arc of acurve, where the arc or the chord faces the seam, or (e) having acomplex geometry that refracts and/or reflects unwanted light indirections are non-orthogonal to the front major surfaces of the lightguides performs the function of reducing visibility of the seam.

In the examples of light redirecting element 315 described above withreference to FIGS. 10A, 10B and 11-15, micro-optical elements configuredto redirect unwanted light emitted from seam towards the observer indirections that reduce the visibility of the unwanted light to theobserver may be located at one or more of the surfaces thereof.Micro-optical elements are features of well-defined shape that are smallrelative to the linear dimensions of the surface at which they arelocated. The smaller of the length and width of a micro-optical elementis less than one-tenth of the larger of the linear dimensions of thesurface, and the larger of the length and width of the micro-opticalelement is less than one-half of the smaller of the linear dimensions ofthe surface. The length and width of the micro-optical element aremeasured in a plane parallel to the surface for flat surfaces, or alonga surface contour for non-flat surfaces. Thus, a light redirectingelement aligned with the seam and having micro-optical elements at oneof more its surfaces performs the function of reducing visibility of theseam.

The examples of light redirecting element 315 described above withreference to FIGS. 10A, 10B and 11-15 have a constant cross-sectionalarea along seam 245 a. In other examples (not shown), the lightredirecting element is tapered such that its cross-sectional areadecreases with increasing distance from light input edges 235. In someembodiments, the light redirecting element tapers to a zerocross-sectional area part-way between the light input edges and endedges 240. Tapering light redirecting element 315 takes account of theway in which the intensity of the light within the light guides 210decreases with increasing distance from the light input edges. Thus, alight redirecting element aligned with the seam and having across-sectional area that decreases with increasing distance from thelight input edge performs the function of reducing visibility of theseam.

Although not illustrated in the figures, the light redirecting element315 additionally includes any known supporting structure to support thelight redirecting element 315 in contact with or slightly separated fromthe front major surfaces 215 a, 215 b of adjacent light guides 210 a,210 b at the seam 245 a between the adjacent light guides. In anexample, light redirecting element 315 includes supports (not shown)that rest on the front major surfaces 215 a, 215 b of adjacent lightguides 210 a, 210 b.

In one embodiment, the light redirecting element 315 is constructed of areflective material, such as a diffusely-reflective material (e.g.,plastic) or a specularly-reflective material (e.g., metal), or amaterial covered with a diffusely- or specularly-reflective film orcoating. In another embodiment, the light redirecting element 315 isconstructed of a transparent or translucent material such as glass orplastic.

The embodiments of modular light-emitting panel assembly 200 to bedescribed next with reference to FIGS. 16-18 reduce visibility of a seambetween adjacent light guides by increasing the lateral spread of theintensity spike resulting from unwanted light extraction at the seams245 between adjacent light guides 210. Increasing the lateral spread ofthe seam reduces the maximum of the intensity spike and thereforereduces the visibility of the seam.

FIG. 16 shows an embodiment in which the side edge 230 a of light guide210 a is substantially planar and is oriented non-orthogonally to theback major surface 220 a of light guide 210 a, while the side edge 225 bof the adjacent light guide 210 b is substantially planar and isoriented relative to the back major surface 220 b of light guide 210 bat an angle that is complementary to the angle of the side edge 230 a.Adjacent light guides having abutting side edges at complementary,non-orthogonal angles to the back major surfaces of the light guidesperform the function of reducing visibility of the seam.

FIG. 17 shows an embodiment in which the side edge 230 a of light guide210 a has a V-shaped protrusion 320, while the side edge 225 b of theadjacent light guide 210 b has a complementary V-shaped recess 325 toreceive and mate with the V-shaped protrusion 320 of side edge 230 a oflight guide 210 a. FIG. 18 shows an embodiment in which the side edge225 b of light guide 210 b has a convex protrusion 330, while the sideedge 230 a of adjacent light guide 210 a has a complementary concaverecess 335 to receive and mate with the convex protrusion 330 of theside edge 225 b of the light guide 210 b. Adjacent light guides havingabutting side edges shaped to provide V-shaped or curved protrusions andcomplementary recesses perform the function of reducing visibility ofthe seam. The configurations of the side edges 230 a, 225 b of lightguides 210 a, 210 b, respectively, described above with reference toFIGS. 16-18 spread seam 245 a laterally in a direction orthogonal to thes. Increasing the lateral spread of the seam reduces the maximum of theintensity spike and therefore reduces the visibility of the seam. Thus,each of the above-described side edge configurations that overlap thelight guides at the seam performs the function of reducing visibility ofthe seam.

FIG. 19 shows another embodiment in which a visibility-reducing patternis located on one or more selected areas of back reflector 265 to reducethe visibility of seam 245 a when panel assembly 200 is illuminated. Inthe example shown in FIG. 19 a visibility-reducing pattern 405 a islocated on a selected area of the surface of back reflector 265 facinglight guides 210 and in alignment with seam 245 a between light guides210 a and 210 b. Visibility-reducing pattern 405 a is configured toabsorb and/or redirect unwanted light emitted from seam 245 a towardsback reflector 265. Without visibility-reducing pattern 405 a, backreflector 265 would reflect such unwanted light towards the observer.Some embodiments of visibility-reducing pattern 405 a arelight-absorbing. In this case, visibility-reducing pattern 405 a absorbsthe unwanted light emitted from seam 245 a, which reduces visibility ofthe unwanted light to the observer. Other embodiments ofvisibility-reducing pattern 405 a are light-redirecting. Herelight-redirecting means light scattering and/or light-redirecting in oneor more specific directions. In this case, visibility-reducing pattern405 a redirects the unwanted light emitted from seam 245 a in otherdirections that reduce visibility of the unwanted light to the observer.Such directions are non-orthogonal to the major surfaces of the lightguides. Thus, back reflector 265 having a light absorbing pattern 405 aor a light redirecting pattern 405 a in alignment with seam 245 aperforms the function of reducing visibility of the seam. Although FIG.19 shows back reflector 265 as having a single visibility-reducingpattern 405 a located in alignment with seam 245 a, back reflector 265typically has a visibility-reducing pattern located in alignment witheach of the seams 245.

Visibility-reducing pattern 405 can be produced in a variety of waysincluding, without limitation, pad printing, silk screen printing, inkjet printing, a heat transfer film process or another suitable process.Visibility-reducing pattern 405 a may be printed on back reflector 265using a wide spectrum of paints, inks, coatings, epoxies, or the like,ranging from glossy to matte and transparent to opaque in anycombination, and may employ dithering and half-tone separationtechniques to vary coverage. Visibility-reducing pattern 405 a mayinclude multiple layers that differ in index of refraction.

In an example, visibility-reducing pattern 405 a is formed byappropriately texturing part of the tool used to mold back reflector 265as a separate component or as an integral part of tray 205. In anotherexample, light diverting pattern is formed by embossing after backreflector 265 has been formed as an individual component or as part oftray 205. Optionally, a reflective or light-absorbing coating applied tothe pattern formed by molding or embossing to complete the production ofvisibility-reducing pattern 405 a.

Visibility-reducing pattern 405 a can include features that vary indensity, size, shape (e.g., dots, polygons, squares, diamonds, ellipses,stars, randomly-varying shapes), color, opacity, index of refraction,absorptance, area coverage and/or another suitable property to divertthe light emitted from seam 245 a in a manner that reduces visibility ofthe seam. For example, by increasing the size and/or density of thefeatures of visibility-reducing pattern 405 a, the visibility-reducingpattern can be made to absorb more of the unwanted light emitted fromseam 245 a. This reduces visibility of the unwanted light output fromseam 245 a. Thus, back reflector 265 having a varying light absorbingpattern 405 a or a varying light redirecting pattern 405 a in alignmentwith seam 245 a performs the function of reducing visibility of theseam. In another embodiment, visibility-reducing pattern 405 has awidthwise-varying absorptance having a maximum at a location inalignment with seam 245 a and that decreases with increasing distancefrom the seam in a direction orthogonal to the length of the seam.

The features in visibility-reducing pattern 405 a can also vary indensity, size, shape (e.g., dots, polygons, squares, diamonds, ellipses,stars, randomly-varying shapes), color, opacity, index of refraction,absorptance, area coverage, and/or another suitable property widthwiseand lengthwise (i.e., in directions orthogonal and parallel to thelength of seam 245 a) in visibility-reducing pattern 405 a to vary thediversion of the unwanted light emitted from seam 245 a. Typically, theintensity of the light in light guides 210 a, 210 b is greater closer tolight sources 250 than further away from the light sources. Accordingly,a lengthways-varying visibility-reducing pattern may be used to adjustfor such intensity variations in the light within the light guides (and,hence, in the intensity of the unwanted light emitted from the seambetween adjacent light guides) to obtain a nominally-constant visibilityof the unwanted light along the length of the seam. In one embodiment,the density and/or size of the features of visibility-reducing pattern405 a is decreased as the distance from light source 250 increases toprovide a more-uniform intensity of the unwanted light emitted from seam245 a. In another embodiment, visibility-reducing pattern 405 aincreases in absorptance with increasing distance from light source 250to provide a more-uniform output of unwanted light from seam 245 a.Thus, back reflector 265 having, in alignment with seam 245 a, a lightabsorbing pattern 405 a or a light redirecting pattern 405 a that varieslengthwise or widthwise or lengthwise and widthwise performs thefunction of reducing visibility of the seam.

In another embodiment shown in FIG. 20, modular light-emitting panelassembly 200 includes a transparent plate 505 juxtaposed with the frontmajor surface 215 of light guides 210. Transparent plate 505 has a frontmajor surface 510 and a back major surface 515, which faces the frontmajor surface 215 of light guides 210. In this example, transparentplate 505 includes a visibility-reducing pattern 520 a in selected areasof the back major surface 515 of the transparent plate. In the exampleshown, a visibility-reducing pattern 520 a is located on the back majorsurface 515 of transparent plate 505 in alignment with seam 245 a.Visibility-reducing pattern 520 a is configured to absorb and/orredirect unwanted light emitted from seam 245 a towards the observer toother directions that reduce visibility of the unwanted light to theobserver. Such directions are non-orthogonal to the major surfaces ofthe light guides. Transparent plate 505 is mounted in tray 205 (FIG. 1A)in a manner that causes it to apply pressure to light guides 210 in adirection orthogonal to the front major surface 215 of the light guides.The pressure assists in aligning the light guides in this orthogonaldirection to reduce deviations from coplanarity of the front majorsurfaces 215 of the light guides. Such deviations would make the seam245 a highly visible. Thus, a transparent plate 505 juxtaposed with thefront major surfaces 215 of light guides 210 a, 210 b that appliespressure to reduce deviations from coplanarity of front major surfaces215 a, 215 b performs the function of reducing visibility of the seam.

In another embodiment, visibility-reducing pattern 520 a is provided onthe front major surface 510 of transparent plate 505 in alignment withseam 245 a. In another embodiment, respective instances ofvisibility-reducing pattern 520 a are provided on the front majorsurface 510 and the back major surface 515 of transparent plate 505 inalignment with seam 245 a. Thus, a transparent plate 505 that isjuxtaposed with the front major surface 215 of light guides 210 a, 210 band that includes a visibility-reducing pattern 520 a in alignment withseam 245 a on the front major surface 510 thereof, or on the back majorsurface 515 thereof, or on both the front major surface and the backmajor surface thereof performs the function of reducing visibility ofthe seam.

In another embodiment, a visibility-reducing pattern similar to thosejust described is located on a diffuser plate, instead of on atransparent plate, in alignment with seam 245 a. In another embodiment,a visibility-reducing pattern similar to those just described is locatedon a transparent film or a diffuser film, instead of on a transparentplate, in alignment with seam 245 a. Thus, a diffuser plate, a diffuserfilm or a transparent film that is juxtaposed with the front majorsurface 215 of light guides 210 a, 210 b and that includes avisibility-reducing pattern in alignment with seam 245 a on the frontmajor surface thereof, or on the back major surface thereof, or on boththe front major surface and the back major surface thereof performs thefunction of reducing visibility of the seam.

In another embodiment shown in FIG. 21, panel assembly 200 includes atransparent plate 505 having a visibility-reducing pattern 520 a alignedwith seam 245 a juxtaposed with the front major surfaces 215 of lightguides 210 a, 210 b, and a back reflector 265 having avisibility-reducing pattern 405 a aligned with seam 245 a juxtaposedwith the back major surfaces 220 of light guides 210 a, 210 b. Thus, atransparent plate 505 juxtaposed with the front major surfaces 215 oflight guides 210 a, 210 b that includes a visibility-reducing pattern520 a aligned with seam 245 a on the front major surface 510 thereof, oron the back major surface 515 thereof, or on both the front majorsurface and the back major surface thereof and a back reflector 245having a visibility-reducing pattern 405 a aligned with seam 245 ajuxtaposed with the back major surfaces 220 of the light guidescollectively perform the function of reducing visibility of the seam.

The seam visibility reduction techniques described herein may also beapplied to seams between the abutted end edges of light guides arrangedin a two-dimensional array.

Two or more of the above-described structures that perform the functionof reducing visibility of the seam can be used in combination with eachother to reduce visibility of the seam when panel assembly 200 isilluminated. For example, a film similar to film 305 described abovewith reference to FIGS. 8A and 8B interposed between the side edges 230a and 225 b of light guides 210 a and 210 b, respectively, may be usedin combination with a film strip similar to film strip 310 describedabove with reference to FIG. 9 covering seam 245 a to reduce thevisibility of seam 245 a.

Because modular light-emitting panel assembly 200 is composed of lightguides 210, each of which is edge lit by an independently-controllablelight source 250, panel assembly 200 can be used to back light liquidcrystal displays (LCDs) having advanced features. An LCD is an exampleof an array of light valves. The implementations of light valve arraysare known and may be back lit using embodiments of the modularlight-emitting panel assembly described herein.

For example, the respective light source 250 edge lighting each lightguide 210 in panel assembly 200 can be configured to provide activecolor correction. For example, active color correction refers tomatching the spectra of the light edge lighting the light guides in thelighting assembly to prevent color differences that would make themodular structure of the lighting assembly apparent to the observer. Toaccomplish this, each light guide 210 includes a sensor (not shown) tosense the intensity and spectrum of the light in the light guide 210.Based on the intensity and spectrum sensed by the sensor, the lightoutput of solid-state light emitters of different colors constitutingthe respective light source 250 edge lighting each light guide 210 canbe controlled to change the intensity and spectrum of the light input tothe light guide. In one example, the solid-state light emitters 252constituting the light source 250 that edge lights each light guide 210are controlled such that the intensity and spectrum of the light edgelighting the light guide is the same as the intensity and spectrum ofthe light edge lighting the other light guides. In another example, thesolid-state light emitters 252 constituting the light source 250 edgelighting each light guide are controlled such that the spectrum of thelight edge lighting the light guide conforms to a standard spectrum. Inanother example, the solid-state light emitters 252 constituting thelight source 250 edge lighting each light guide are controlled such thatthe intensity and spectrum of the light edge lighting the light guide isoptimized in accordance with the brightness and color represented by avideo signal portion provided to a slice of the LCD back lit by lightextracted from the light guide.

In an example, a common sensor is used to determine the spectrum of thelight edge lighting all the light guides. In this case, a sample oflight from each light guide is conveyed to the sensor though an opticaldevice, such as an optical fiber or a light guide. In this embodiment,the light sampled from the light guides can be temporally separated fromone another at the sensor by pulsing the light sources 250 edge lightingthe respective light guides with an appropriate timing. Additionally oralternatively, the light samples from the light guides can be spatiallyseparated from one another at the sensor by conveying the light samplefrom each light guide to the sensor by a separate optical fiber or adifferent portion of the light guide and using a segmented sensor withat least one segment per light guide. Alternatively, a non-segmentedsensor can be used together with a mechanism that moves the sensor andoptical fibers or light guide relative to one another. In addition, inan embodiment in which a light source 250 composed of multiplesolid-state light emitters edge lights a single light guide, the sensorcan sense a sample of light from each individual solid-state lightemitter and corresponding individual adjustments to the light output ofthe light source can be made by pulsing the constituent solid-statelight emitters with appropriate timing that temporally separates thelight samples reaching the sensor from each solid-state light emitter.

Panel assembly 200 can also be configured to provide progressiveillumination scanning for use with light valve arrays that employprogressive refresh scanning. Since light sources 250 illuminating thelight guides 210 are independently controllable, the light sources 250can be turned on and off to permit selective illumination of the lightguides 210.

FIGS. 22A-22D show an example of a progressive illumination scanningsequence and FIGS. 23A-23D show another example of a progressiveillumination scanning sequence that can be implemented using panelassembly 200. FIGS. 22A-22D and FIGS. 23A-23D show only parts ofprogressive illumination scanning sequences, but the remainder of thesequences can be deduced from the drawings and the description below. Inthe FIGS. 22A-22D and FIGS. 23A-23D, a light guide 210 whose respectivelight source 250 is turned on is shown in white. Further, although theexample of panel assembly 200 shown in FIGS. 22A-22D and FIGS. 23A-23Dhas nine light guides 210, panel assembly 200 can have more or fewerlight guides 210, as described above.

FIGS. 22A-22D show part of an example of a progressive illuminationscanning sequence implemented using panel assembly 200. Initially, asshown in FIG. 22A, the light sources 250 of all the light guides 210 butlight guide 210 a are turned on. While light guide 210 a is turned off,the slice of the LCD backlit by light guide 210 a is refreshed. Next, asshown in FIG. 22B, the light source of light guide 210 a turns back onand that of light guide 210 b turns off, so that the light sources ofall the light guides 210 but light guide 210 b are turned on. Whilelight guide 210 b is turned off, the slice of the LCD backlit by lightguide 210 b is refreshed. Next, as shown in FIG. 22C the light source oflight guide 210 b turns back on and that of light guide 210 c turns off,so that the light sources of all the light guides 210 but light guide210 c are turned on. While light guide 210 c is turned off, the slice ofthe LCD backlit by light guide 210 c is refreshed. Next, as shown inFIG. 22D the light source of light guide 210 c turns back on and that oflight guide 210 d turns off, so that the light sources of all the lightguides 210 but light guide 210 d are turned on. While light guide 210 dis turned off, the slice of the LCD backlit by light guide 210 d isrefreshed. The sequence continues in a similar manner until therespective light sources of light guides 210 e-i have been sequentiallyturned off and the corresponding slices of the LCD have been refreshed.The sequence is then continuously repeated to provide progressiveillumination scanning.

FIGS. 22A-22D show an example of a progressive illumination scanningsequence. Other progressive illumination sequences are possible. FIGS.23A-23D show part of another example of a progressive illuminationscanning sequence implemented using panel assembly 200. Initially, asshown in FIG. 23A, the light source 250 of only light guide 210 a isturned on, and the respective light sources 250 of the remaining lightguides 210 are turned off. While light guide 210 a is turned on, theslice of the LCD backlit by light guide 210 b is refreshed. Next, asshown in FIG. 23B, the light source of light guide 210 b is turned on,the light source of light guide 210 a is turned off, and the lightsources of the remaining light guides 210 remain turned off. While lightguide 210 b is turned on, the slice of the LCD backlit by light guide210 c is refreshed. Next, as shown in FIG. 23C, the light source oflight guide 210 c is turned on, the light source of light guide 210 b isturned off, and the light sources of the remaining light guides 210remain turned off. While light guide 210 c is turned on, the slice ofthe LCD backlit by light guide 210 d is refreshed. Next, as shown inFIG. 23D, the light source of light guide 210 d is turned on, the lightsource of light guide 210 c is turned off, and the light sources of theremaining light guides 210 remain turned off. While light guide 210 d isturned on, the slice of the LCD backlit by light guide 210 e isrefreshed. The sequence continues in a similar manner until therespective light sources of light guides 210 e-i have been sequentiallyturned on and slices of the LCD that are illuminated subsequently havebeen refreshed. The sequence is then continuously repeated to provideprogressive illumination scanning.

Additionally, the panel assembly 200 can be configured to performlocalized active dimming. Since the light sources 250 are independentlycontrollable, the light source 250 edge lighting each of the lightguides 210 can be dynamically controlled to control the intensity oflight illuminating the respective light guide 210 depending on thebrightness represented by the portion of the video signal displayed bythe slice of the LCD backlit by the respective light guide. In anexample, the light output of the light source 250 edge lighting a lightguide 210 that back lights a slice of the LCD displaying ahigh-brightness portion of an image is increased, whereas the lightoutput of the light source 250 edge lighting another of the light guides210 that back lights a slice of the LCD that displays a low-brightnessportion of the image is decreased. FIG. 24 shows an image in which thelight output by light sources 250 to edge light light guides 210 f-i isdecreased in intensity to display the darker water region of the imagedisplayed by the LCD, whereas the light output by light sources 250 toedge light light guides 210 a-e is increased in intensity to display thebrighter sky region of the image displayed by the LCD. In anotherexample, when an image having a width/height aspect ratio greater thanthe width/height aspect ratio of the LCD is displayed, the light sourcesof the light guides 210 backlighting the dark slices of the LCD areturned off.

In addition to intensity, the spectrum of the light that edge lightseach light guide 210 can be individually controlled depending on thechrominance represented by the portion of the video signal displayed theslice of the LCD backlit by the respective light guide. For example,when one or more slices of the image displayed by the LCD are rich inred, then in the light sources 250 that edge light the light guides 210that back light such slices, the constituent solid-state light emittersthat output red light can be controlled to increase the intensity of thered light to produce a more vibrant image.

Furthermore, panel assembly 200 can permit selective illumination,including sequential illumination, of solid-state light emitters 252that generate light of each color. Alternatively, all of the lightsources 250 can be turned on and off together to permit flashing of theentire panel assembly 200.

We claim:
 1. A light-emitting panel assembly, comprising: a first lightguide and a second light guide, each light guide having a light inputedge, opposed side edges, opposed major surfaces and a pattern of lightextracting elements at at least one of the major surfaces, one of theside edges of the first light guide juxtaposed with one of the sideedges of the second light guide and defining a seam between the firstlight guide and the second light guide; and a first light sourceadjacent the light input edge of the first light guide and a secondlight source adjacent the light input edge of the second light guide,the first and second light sources configured to respectively edge lightthe first light guide and the second light guide such that lightpropagates along each light guide by total internal reflection at themajor surfaces thereof for extraction from the light guide by the lightextracting elements; wherein at least a portion of the juxtaposed sideedge of the first light guide is at a non-orthogonal angle relative tothe major surfaces of the first light guide and at least a portion ofthe juxtaposed side edge of the second light guide is at anon-orthogonal angle relative to the major surfaces of the second lightguide.
 2. The light-emitting panel assembly of claim 1, wherein thejuxtaposed side edges of the first light guide and the second lightguide are planar and oriented at complementary, non-orthogonal angles tothe major surfaces of the light guides.
 3. The light-emitting panelassembly of claim 1, wherein the juxtaposed side edges of the firstlight guide and the second light guide define a V-shaped protrusion anda complementary V-shaped recess, respectively.
 4. The light-emittingpanel assembly of claim 1, wherein the juxtaposed side edges of thefirst light guide and the second light guide define a convex protrusionand a complementary concave recess, respectively.
 5. The light-emittingpanel assembly of claim 1, further comprising a diffusely-reflectivecoating or an anti-reflective coating on one or both of the juxtaposedside edges of the first light guide and the second light guide.
 6. Thelight-emitting panel assembly of claim 1, further comprising lightreflective or refractive structures on one or both of the juxtaposedside edges of the first light guide and the second light guide.
 7. Thelight-emitting panel assembly of claim 1, further comprising a lightredirecting element offset from the seam in a direction orthogonal tothe major surfaces, the light redirecting element configured to redirectat least a portion of light emitted from the seam in other directionsnon-orthogonal to the major surfaces.
 8. A light-emitting panelassembly, comprising: a first light guide and a second light guide, eachlight guide having a light input edge, opposed side edges, opposed majorsurfaces and a pattern of light extracting elements at at least one ofthe major surfaces, one of the side edges of the first light guidejuxtaposed with one of the side edges of the second light guide anddefining a seam between the first light guide and the second lightguide; a first light source adjacent the light input edge of the firstlight guide and a second light source adjacent the light input edge ofthe second light guide, the first and second light sources configured torespectively edge light the first light guide and the second light guidesuch that light propagates along each light guide by total internalreflection at the major surfaces thereof for extraction from the lightguide by the light extracting elements; and one or more lightredirecting elements at one or both of the juxtaposed side edges, theone or more light redirecting elements configured to reduce visibilityof the seam when the light sources illuminate the light guides.
 9. Thelight-emitting panel assembly of claim 8, wherein the one or more lightredirecting elements comprises a diffusely-reflective coating on one orboth of the juxtaposed side edges of the first light guide and thesecond light guide.
 10. The light-emitting panel assembly of claim 8,wherein one or more light redirecting elements comprises ananti-reflective coating on one or both of the juxtaposed side edges ofthe first light guide and the second light guide.
 11. The light-emittingpanel assembly of claim 8, wherein one or more light redirectingelements comprises light reflective or refractive structures on one orboth of the juxtaposed side edges of the first light guide and thesecond light guide.
 12. A light-emitting panel assembly, comprising: afirst light guide and a second light guide, each light guide having alight input edge, opposed side edges, opposed major surfaces and apattern of light extracting elements at at least one of the majorsurfaces, one of the side edges of the first light guide juxtaposed withone of the side edges of the second light guide and defining a seambetween the first light guide and the second light guide; a first lightsource adjacent the light input edge of the first light guide and asecond light source adjacent the light input edge of the second lightguide, the first and second light sources configured to respectivelyedge light the first light guide and the second light guide such thatlight propagates along each light guide by total internal reflection atthe major surfaces thereof for extraction from the light guide by thelight extracting elements; and a light redirecting element offset fromthe seam in a direction orthogonal to the major surfaces, the lightredirecting element configured to redirect at least a portion of lightemitted from the seam in other directions non-orthogonal to the majorsurfaces.
 13. The light-emitting panel assembly of claim 12, wherein thelight redirecting element has a triangular cross-section where thetriangle has an apex aligned with and facing the seam.
 14. Thelight-emitting panel assembly of claim 13, wherein surfaces of thetriangle that form the apex are concave.
 15. The light-emitting panelassembly of claim 12, wherein the light redirecting element has aT-shaped cross section, where the T shape has a base aligned with andfacing the seam.
 16. The light-emitting panel assembly of claim 12,wherein the light redirecting element has a cross-section bounded by achord and an intersecting arc of a curve, where the arc is aligned withand faces the seam.
 17. The light-emitting panel assembly of claim 12,wherein the light redirecting element has a cross-section bounded by achord and an intersecting arc of a curve, where the chord is alignedwith and faces the seam.
 18. The light-emitting panel assembly of claim12, wherein the light redirecting element has a rectangularcross-section, where the rectangle has a grooved surface aligned withand facing the seam.
 19. The light-emitting panel assembly of claim 12,wherein the light redirecting element comprises a surface facing theseam and micro-optical elements at at least part of the surface.
 20. Thelight-emitting panel assembly of claim 12, wherein the light redirectingelement has a cross-sectional area that decreases with increasingdistance from the light input edges of the light guides.